Luiselli, D. | Search bioRxiv

bioRxiv2017

Impact of non-LTR retrotransposons in the differentiation and evolution of Anatomically Modern Humans

Transposable Elements are biologically important components of eukaryote genomes. In particular, non-LTR retrotransposons (N-LTRrs) extensively shaped the human genome throughout evolution. In this study, we compared retrotransposon insertions differentially present in the genomes of Anatomically Modern Humans, Neanderthals, Denisovans and Chimpanzees, in order to assess the possible impact of retrotransposition in the differentiation of the human lineage. Briefly, we first identified species-specific N-LTRrs and established their distribution in present day human populations. These analyses shortlisted a group of N-LTRr insertions that were found exclusively in Anatomically Modern Humans. Notably, these insertions targeted genes more frequently than randomly expected and are associated with an increase in the number of transcriptional/splicing variants of those genes they inserted in. The analysis of the functionality of genes targeted by human-specific N-LTRr insertions seems to reflect phenotypic changes that occurred during human evolution. Furthermore, the expression of genes containing the most recent N-LTRr insertions is enriched in the brain, especially in undifferentiated neurons, and these genes associate in networks related to neuron maturation and migration. Additionally, we also identified candidate N-LTRr insertions that have likely produced new functional variants exclusive to modern humans, which show traces of positive selection and are now fixed in all present-day human populations. In sum, our results strongly suggest that N-LTRr impacted our differentiation as a species and have been a constant source of genomic variability all throughout the evolution of the human lineage.

genomics↗

bioRxiv2016

The Tell-Tale Genome

Observable patterns of cultural variation are consistently intertwined with demic movements, cultural diffusion, and adaptation to different ecological contexts (Cavalli-Sforza and Feldman 1981; Boyd and Richerson 1985). The quantitative study of gene-culture co-evolution has focused in particular on the mechanisms responsible for change in frequency and attributes of cultural traits, on the spread of cultural information through demic and cultural diffusion, and on detecting relationships between genetic and cultural lineages. Here, for the first time, we make use of worldwide whole-genome sequences (Pagani et al. 2016) to assess the impact of demic diffusion on cultural diversity, focusing on the variability observed in folktale traditions (N=596) (Uther 2004) in Eurasia and Africa. We show that at small geographic scales (<=5000 km) there is a strong correlation between folktale and genomic distance when the effect of geography is corrected, while geographic distance has no independent effect on the distribution of folkloric narratives at the same spatial scale. This points to demic processes (i.e. population movement and replacement) as the main driver of folktale transmission at limited geographic ranges. The role of population movements becomes more apparent when regions characterized by episodes of directional expansions, such as the Neolithization of West Eurasia, are examined. Furthermore, we identify 89 individual tales which are likely to be predominantly transmitted through demic diffusion, and locate putative focal areas for a subset of them.

evolutionary biology↗